That's the same thing that happens to me, everytime I stand up I get very dizzy. Do you have headaches and nausea too? My blood pressure is usually pretty low. My family Doctor did some blood work but everything seemed fine. My cortisol for the morning was 19.0 fasting Glucose was 94. Potassium was 3.6 Sodium was 143 and TSH 3rd generation value was 2.65. But I keep trying to tell them something is seriously wrong.